Abstract
Infection with Plasmodium falciparum and vivax cause most cases of malaria. Emerging resistance to current antimalarial medications makes new drug development imperative. Ideally a new antimalarial drug should treat both falciparum and vivax malaria. Because malaria parasites are purine auxotrophic, they rely on purines imported from the host erythrocyte via Equilibrative Nucleoside Transporters (ENTs). Thus, the purine import transporters represent a potential target for antimalarial drug development. For falciparum parasites the primary purine transporter is the P. falciparum Equilibrative Nucleoside Transporter Type 1 (PfENT1). Recently we identified potent PfENT1 inhibitors with nanomolar IC50 values using a robust, yeast-based high throughput screening assay. In the current work we characterized the Plasmodium vivax ENT1 (PvENT1) homologue and its sensitivity to the PfENT1 inhibitors. We expressed a yeast codon-optimized PvENT1 gene in Saccharomyces cerevisiae. PvENT1-expressing yeast imported both purines ([3H]adenosine) and pyrimidines ([3H]uridine), whereas wild type (fui1δ) yeast did not. Based on radiolabel substrate uptake inhibition experiments, inosine had the lowest IC50 (3.8 μM), compared to guanosine (14.9 μM) and adenosine (142 μM). For pyrimidines, thymidine had an IC50 of 183 μM (vs. cytidine and uridine; mM range). IC50 values were higher for nucleobases compared to the corresponding nucleosides; hypoxanthine had a 25-fold higher IC50 than inosine. The archetypal human ENT1 inhibitor 4-nitrobenzylthioinosine (NBMPR) had no effect on PvENT1, whereas dipyridamole inhibited PvENT1, albeit with a 40 μM IC50, a 1000-fold less sensitive than human ENT1 (hENT1). The PfENT1 inhibitors blocked transport activity of PvENT1 and the five known naturally occurring non-synonymous single nucleotide polymorphisms (SNPs) with similar IC50 values. Thus, the PfENT1 inhibitors also target PvENT1. This implies that development of novel antimalarial drugs that target both falciparum and vivax ENT1 may be feasible.
| Original language | English |
|---|---|
| Pages (from-to) | 1-11 |
| Number of pages | 11 |
| Journal | International Journal for Parasitology: Drugs and Drug Resistance |
| Volume | 6 |
| Issue number | 1 |
| DOIs | |
| State | Published - Apr 1 2016 |
Bibliographical note
Publisher Copyright:© 2015 The Authors.
Funding
We thank David Pierce for expert technical assistance and Andrea Lopez and Adi Berman for contributions to the project while working in the Einstein Summer Undergraduate Research Program. RD and IJF were supported in part by the NIGMS Medical Scientist Training Program grant T32-GM007288 . This work was supported by funds from the Albert Einstein College of Medicine and from NIH R01AI116665 to MHA. The funders had no role in the study design, collection or analysis of data or in writing and submission of this manuscript.
| Funders | Funder number |
|---|---|
| Albert Einstein Cancer Center of the Albert Einstein College of Medicine of Yeshiva University | |
| National Institutes of Health (NIH) | |
| National Institute of Allergy and Infectious Diseases | R01AI116665 |
| NIGMS Medical Scientist Training Program | T32-GM007288 |
| National Institute of General Medical Sciences DP2GM119177 Sophie Dumont National Institute of General Medical Sciences | T32GM007288 |
| UK Industrial Decarbonization Research and Innovation Centre | 41095 |
Keywords
- Drug development
- Malaria
- Nucleoside/nucleobase transport
- Parasite
- Plasmodium vivax
- Purines
- Single-nucleotide polymorphism (SNP)
- Transporter
ASJC Scopus subject areas
- Parasitology
- Infectious Diseases
- Pharmacology (medical)